Air sampling apparatus for collecting airborne contaminants such as toxic mists, dusts, particulates, gases and vapors are known. Typically, such equipment is connected to a source of vacuum, e.g., a pump, whereby the airborne contaminants may be drawn into the equipment through the action of the pump. The pumps associated with air sampling equipment, commonly known as personal sampling pumps, are lightweight and portable such that they may be conveniently worn by an industrial hygienist or other worker that must perform activity in environments whose ambient air may be contaminated and/or hazardous.
Some air sampling apparatus are capable of simultaneously taking multiple air samples in parallel. Early versions of instruments of this type possessed no means for independently controlling individual sampling port vacuum flow rate. As a result, adjustment of the vacuum flow rate of one sampling port in such devices disturbed the vacuum flow rates previously set for the other sampling ports. In presently available parallel sampling apparatus, controlling the flow rates of the sampling ports is incorporated as part of the sampling pump. Consequently, the sampling apparatus of this latter class are capable of fitting and functioning with only one specific pump. Moreover, the remote location of the sampling ports from the regulator makes the vacuum flow rate partially dependent on the diameter and the length of the sample line connecting them. Depending on the flow rates in the sampling ports and the pressure drop in the sample line, these apparatus often require an iterative process to set and balance the flows through the sampling ports.
A need exists, therefore, for a multiple sampling port personal air sampling apparatus capable of simultaneously taking a plurality of independently controllable ambient air samples in parallel. This can be accomplished if the regulator for controlling individual sampling port vacuum is incorporated into the sampling apparatus rather than in the sampling pump associated therewith. So constructed, such apparatus would be capable of functioning with virtually any personal sampling pump while enabling independent control of each of the multiple sampling ports. Further, the apparatus would provide enhanced control and adjustability by regulating air flow essentially at the load site, i.e., proximate the sampling ports, rather than at a more remote location such as at the pump.